1. Technical Field
The present invention relates to a method of controlling an endoscope and an endoscope.
2. Description of the Related Art
Recently, an endoscope is used which applies narrow-band light in a specific narrow wavelength band to biological mucosa tissue to obtain tissue information at a desired depth of the body tissue, i.e., perform a so-called special light observation (see JP 2002-34893 A (corresponding to US 2003/0176768 A, US 2008/0281154 A and US 2008/0294105 A))). In such an endoscope, it is possible to easily visualize body information, which cannot be obtained in a normal observation image, such as microstructure of a new blood vessel generated in a mucosa layer or submucosa layer and enhancement of a lesion part. For example, for a cancer lesion part that is an object to be observed, when blue narrow-band light is applied to the mucosa tissue, it is possible to observe micro blood vessels or microstructure of superficial layer more specifically. Therefore, it is possible to diagnose the lesion part more exactly.
However, in the special light observation, the observation is performed with a captured image that is obtained when the narrow-band light is applied to the body tissue. Hence, even when an intensity of illumination of the narrow-band light is appropriately adjusted at the observation time in a closeup view, it is not possible to obtain an intensity of illumination enough to observe the superficial blood vessels at the observation time in a distant view having a wide angle of view. Due to this, a gain of an imaging section or a display section is adjusted whenever observation conditions such as an observation object or an observation position is changed, thereby enabling the observation to be performed with a proper brightness level. Additionally, in the endoscope of JP 2002-34893 A, the light from a white light source is changed in a time division manner by a color filter, and light (R light, G light, B light) in different wavelength bands are frame-sequentially emitted to perform an imaging. Due to this, in order to obtain an observation image of full colors in real time, it is necessary to combined captured images of plural frames (R frame, G frame, B frame), so that it is difficult to increase a frame rate of the observation image.